VIENNA - US Secretary of State John Kerry arrived in Vienna on Sunday for talks with foreign ministers from the six powers negotiating with Tehran on its nuclear program.

Kerry arrived in the early hours after clinching a deal in Kabul with Afghanistan's presidential candidates to end the country's election crisis.

Iran and the powers - the United States, France, Germany, Britain, Russia and China - aim to reach a long-term deal to end the decade-old nuclear standoff by a July 20 deadline. Many diplomats and analysts believe an extension may be needed in view of the wide gaps in negotiating positions.